The '258 application discloses a power supply system for the distribution of electrical power in a computer facility room which includes a plurality of enclosed electrical plug-in busways located beneath the raised floor of the room. The busways are provided with a main power distribution unit, and power is provided from the busways to equipment, such as computers, via a plug-in cable which is plugged into the busway. The power distribution unit may be configured to provide an uninterrupted power supply, an isolation transformer for protecting sensitive equipment such as computers, and filtering. Accordingly, all of the equipment connected to the busway is provided with "high quality" electrical power which is uninterruptable, isolated and filtered. While this arrangement is desirable if all of the equipment connected to the busway is sensitive equipment such as computers, this arrangement can become very costly if such "high quality" electrical power must also be provided to other non-sensitive equipment (e.g. motors, lights, resistive heat) connected to the busway which does not require "high quality" electrical power.
The unnecessary provision of uninterruptable power to all of the equipment connected to a busway requires a larger and more costly uninterrupted power supply at the power distribution unit. Additionally, the provision of isolation and filtering to equipment which does not require this type of power conditioning, requires the use of larger and more costly isolation transformers and filtering circuits in the power distribution unit.
Accordingly, it would be advantageous to provide a busway and busway plug-in arrangement which allows selective provision of "high quality" (conditioned) or "medium quality" (partially conditioned) or "low quality" (non-conditioned) electrical power depending upon the requirements of the equipment connected to an electrical busway. For example, if a sensitive piece of equipment, such as a computer, and a relatively insensitive piece of equipment, such as a fan, are to be connected to a busway, then it would be desirable to provide "high quality" electrical power to the computer via the busway while simultaneously providing "low quality" electrical power to the fan via the same busway.